Technical Abstract:
Soil organic carbon (SOC) content is recognized as a soil quality indicator that is susceptible to degradation with tillage and with biomass removal from the soil surface. In addition to reported benefits of leaving crop residue on the soil surface in preventing soil erosion, providing plant nutrients and reducing rainfall runoffs; the impact of biomass harvesting for energy production on the SOC was pointed out. Reported values of SOC accumulation under no-till or conservation till varied widely from below zero up to 1300 kg/ha/yr depending on the crop type and mean annual temperature. However, very few studies of no-till practice with concurrent management of crop residue removal, from % to 100%, reported negative impact on soil carbon balance with extensive biomass removal. Perennial grasses are strong candidates as a source for biofuel production. These, in turn, will entail very large monoculture fields’ with no-till soil practice and extensive harvesting of residues. These unfavorable conditions may degrade the soil condition by depleting soil’s SOC and nutrients beyond the point of standard fertilization. Thus raising the question of sustainability and, more importantly, challenging the fundamental assertion that the entire cycle of energy production from biofuels, on balance, will reduce the levels of atmospheric carbon dioxide. To monitor soil conditions over vast areas with variable landscapes using current state-of-the-art procedures for soil sampling and analysis by dry combustion presents a formidable task that is labor intensive and time consuming. We propose to implement a new instrument for soil carbon, nitrogen and potassium monitoring in soil that is non-destructive and can be used in either stationary or continuous scanning modes of operation. The instrument senses the elements to an approximate depth of 30 cm and provides a true mean values for an arbitrarily large scanned area, in a stationary mode the analyzed soil mass is larger than 200 kg. It is envisioned that the inelastic neutron scattering (INS) system would be more sensitive to changes in the soil conditions, on annual or semi-annual basis, rather than the currently employed methods that require a three or five years period. We report the results obtained with the INS system used in stationary and scanning modes and discuss its merits.